1. Field of the Invention
The present invention relates to a method for controlling a video display device having multiple signal sources, and more particularly to a method for controlling a video display device having multiple signal sources capable of determining whether a power saving mode is executed according to a signal source selection state.
2. Description of the Prior Art
In compliance with the current trend of multimedia systems, video display devices such as computer monitors having, for example, a liquid crystal display unit for displaying a received video signal, are appearing on the market and are capable of selectively displaying video signals input from multiple signal sources, such as a computer, a television cable, an antenna, and a video cassette recorder.
A video display device capable of being connected to multiple signal sources may include such components as a tuner, a switching unit, a display controller, a liquid crystal display unit, a key input unit, a microcomputer, a power supply, and a power-saving unit.
In a video display device capable of being connected to multiple signal sources and having the above components, the tuner converts a high frequency television signal input through an antenna or cable into an intermediate frequency and the separates a composite video signal from the intermediate frequency for an output. The switching unit selectively outputs one of the composite video signals of the composite video signal input from the tuner and a composite video signal input from an external signal source (e.g., VCR). The display controller carries out signal processing with respect to a first digital RGB video signal or a second digital RGB video signal to be displayed on a screen. The liquid crystal display unit displays images of the digital RGB video signal input from the display controller.
At this time, the microcomputer controls every unit of a system by a key input of a user, and selectively displays on a screen one of a video signal input from the computer (PC), a video signal input from an television antenna or cable, and a video signal input from the video cassette recorder (VCR).
In general, when a user does not use a turned-on computer, the computer recognizes the lack of use and decreases the power consumption to a level less than a predetermined level such that a signal is not output to the video display device, and when the user again uses the computer, without the computer being turned off, the signal previously displayed will again immediately and automatically appear on the video display device.
A video display device having such a power-saving function is realized with a known display power management system (DPMS) in accordance with a standardized scheme of the Video Electronics Standardization Association (VESA), which is operated with the separation of a normal mode and a power-saving mode. The power-saving mode is divided into a standby mode, a suspend mode, and a turn-off mode and is controlled by computer software. The operations of the normal mode and the power-saving mode of a general video display device are describe as below with reference to Table 1 and FIG. 2.
TABLE 1 SAVING/RETURNINGCOMMANDRE-TIMEhorizontalverticalQUIRE-CONSUMP-FORsychroniza-sychroniza-MENTTIONNORMALMODEtiontionSTATEPOWERSTATEnormalyesyesforced100%—standbynoyesoptional 80%shortsuspendyesnoforced15 Wlongoffnonoforced 5 W—
As indicated by Table 1, the VESA standard calls for the computer (PC) to supply to the video display device a horizontal synchronous signal (H.sync) and a vertical synchronous signal (V.sync) when in the normal mode; only the vertical synchronous signal (V.sync) when in the standby mode, only the horizontal synchronous signal (H.sync) when in the suspend mode, and neither the horizontal synchronous signal (H.sync) nor the vertical synchronous signal (V.sync) to the video display device when in the off mode.
In the normal mode, since the horizontal synchronous signal (H.sync) and the vertical synchronous signal (V.sync) are input from the computer (PC), the microcomputer controls the power-saving unit to normally operate each component of the system by supplying a rated voltage output from a power supply to each component of the system.
In the meantime, in the power-saving mode, since one or more signal of the horizontal synchronous signal (H.sync) and the vertical synchronous signal (V.sync) are not input, the microcomputer controls the power-saving unit according to the power-saving mode to decrease the power consumption to a level lower than a predetermined level by cutting off a voltage supplied to each component of the system from the power supply.
As stated above, the video display device having multiple signal sources is converted to the power-saving mode, if there is no key input from a user for a predetermined time, to cut off the supply of an output voltage from the power supply to each component of the system, so that the power assumption is dropped to a level lower than a predetermined level to meet the VESA standard. Even when a video signal input from a television antenna/cable or a video signal input from a video cassette recorder (VCR) is displayed on a screen, the microcomputer is converted to the power-saving mode to cut off a voltage supplied to each component of the power supply if there is no key input for a predetermined time, so a problem is caused in that the driving of each component of the system is stopped.